This invention relates to gas tube protectors.
Gas tube protectors, also known as gas surge limiters, are used extensively in the telecommunications network in order to protect customer premises equipment from excess voltages which result from such causes as lightning strikes. The devices are connected in parallel with the protected equipment and include at least two electrodes, one coupled to a customer line and the other coupled to a ground potential. Between the electrodes is a spark gap which is normally nonconducting so that the protector does not interfere with the usual operation of the customer's equipment. However, if a sufficiently high voltage appears on the line, the device will fire and shunt the excess voltage to ground.
A coating of glass thermionic material is usually provided on the surface of the electrodes to enhance the discharge of the device. One problem with the use of such coatings is that the electrodes would have to be "conditioned" prior to use. That is, a specific firing sequence would be employed in order to produce the right coating composition and to form points of initiation for arcing across the electrode gap. This firing sequence would typically involve applying a 1000 VRMS signal through a 100 ohm limiting resistor for approximately one second with a 0.022 microfarad capacitor in parallel with the gap. This conditioning requires special equipment and also tends to adversely affect the breakdown ranges of the device.
It is, therefore, an object of the invention to produce a gas tube protector which does not require conditioning.